A t higher elevations in well-drained sites, the soils included in this

group are usually noncalcareous and have 6- to 12-inch surface horizons

that are typically grayish-brown (lOYR 5/2, dry) to very dark grayishbrown (lOYR 3/2, moist). For the purposes of this paper they are included with the Alluvial soil group, but in the new system of soil

classification such soils would be placed in frigid families of Haplustolls, Hapludolls, or Haploboralls since they are considered to have mollic

epipedons.

With increasingly poor drainage, at low elevations, these soils lacking mollic epipedons become strongly mottled with both bright and low

chroma mottlings, and the mottling occurs higher in the profile. In the

new system of classification such soils would be considered aquic Haplorthents, but for the purpose of this paper they are included in the

With decreasing age of landscapes, or sharply increasing slope gradient, the strong horizons of secondary calcium carbonate weaken and

these soils grade into Alluvial soils or Regosols ( Orthents or Psamments)

With increasing age of landscape these soils become noncalcareous

in their upper horizons and start to develop horizons of silicate clay

accumulation. Under these conditions they eventually grade into Brown

soils ( Argids ) .

With increasing soil moisture the surface horizons darken and the

horizons of maximum secondary calcium carbonate accumulation move

downward. For the purposes of this paper, soils that have developed

mollic epipedons and have retained a strong horizon of secondary calcium carbonate accumulation are still included in the Calcisol group.

In the new system of classification such soils would be considered to

be Calciustolls. If given sufficient age so that horizons of silicate clay

accumulation can develop, these soils will eventually grade into Chestnut soils (Ustolls).

.

266

D. D. JOHNSON AND A. J . CLINE

J . CHERNOZEMS

These are well-drained, dark-colored, neutral to alkaline soils developing on alluvial fans, mountain sides, or old terrace levels in a

variety of parent materials, but mainly those derived from calcareous

sedimentary rock or bedrock high in bases. Typically they have darkcolored, granular A horizons of low chroma, horizons of secondary silicate clay accumulation, and weak horizons of secondary calcium carbonate accumulation. The following is a description of a typical soil

of this group.

*I

B,

B,ca

Cca

Dark gray (10YR 4/1, dry) to black (10YR 2/1, moist) loam;

moderate to strong fine crumb and granular structure; soft dry,

very friable moist; noncalcareous, pH 7.2; clear wavy boundary.

8-12'' Brown or dark brown (7.5YR 4/2, dry) to very dark brown (7.5YR

2/2, moist) heavy loam; moderate 6ne subangular blocky structure

breaking to medium granules; slightly hard dry, very friable moist;

thin patchy clay films; noncalcareous, pH 7.2; clear smooth

boundary.

12-34" Reddish-brown (5YR 5/4, dry) to (5YR 4/4, moist) heavy clay

loam; weak coarse prismatic structure breaking to moderate coarse

and medium angular blocks; extremely hard dry, very plastic wet;

thick continuous clay films; 5 per cent stone; noncalcareous, pH

7.4; gradual wavy boundary.

3440" Reddish-brown (5YR 5/4, dry to 5YR 4/4, moist) clay loam; weak

to moderate medium angular and subangular blocky structure;

extremely hard dry, very plastic wet; many thin patchy clay films;

10 per cent stone; a weak horizon of secondary calcium carbonate

accumulation with visible calcium carbonate occurring mostly in

large concretions; calcareous, pH 7.8; gradual wavy boundary.

40-80" Light reddish-brown (5YR 6/4, dry) to reddish-brown (5YR 5/4,

moist) stony clay loam; massive; extremely hard dry, plastic wet;

15 per cent stone some of which is well weathered; a moderate

to strong ca horizon with visible calcium carbonate occurring as

large concretions, and in finely divided forms; calcareous, pH 8.0.

0-8"

With decreasing soil temperature, or decreasing effective soil moisture, the surface horizons tend to brighten in chroma and these soils

grade into the Chestnut soils (Ustolls). With increasingly poor degrees

of drainage these soils develop mottling and gleying, and grade into

the Humic Gley soils ( Aquolls ) .

With increasing soil moisture, decreasing soil temperature, and an

increasing proportion of conifers in the vegetative cover, the A horizon

thins and becomes lighter in color and eluvial A2 horizons start to develop. Under these conditions these soils grade into the Gray Wooded

soils (Boralfs), or Degraded Chernozems (Boralfic Argiborolls).

COLORADO MOUNTAIN SOILS

267

K. DEGRADED

CHERNOZEMS

These are well-drained, moderately acid to mildly alkaline soils developing in transitional areas between grasslands and forest on mountain